Then I realize what it is. It's him. Something about him makes me feel like I am about to fall. Or turn to liquid. Or burst into flames.

This quote is referring to a person who has a strong and powerful effect on the speaker. The speaker feels mesmerized and captivated when they are with this person, feeling like they could either fall, turn to liquid, or burst into flames. This means the person’s magnetic presence is overwhelming, making the speaker feel intense emotions but unable to explain why.